Headlight



E. H. HOBBIE.

HEADLIGHT.

APPLICATION FILED SEPTJZ, 191a.

1,3411 28, Patented May 25, 1920.

2 SHEETSSHEET lw r-ww a E. H. HOBBIE.

HEADLIGHT.

APPLICATION FILED SEPT-21, l9l8.

Patented May 25, 1920.

2 SHEETS-SHEET 2.

I nveriioz UNITED srATEs PATENT GFFIQE.

EDWARD H. HOBBIE, F BOONTON, NEW JERSEY, ASSIGNOR TO SAFER/LITE LENS COMPANY, INC., 013 NEW YORK, N. Y., A CQRPORATION OF NEW YORK.

HEADLIGHT.

Specification of Letters Patent.

Patented May 25, 1920.

Continuation of application Serial No. 180,044, filed July 12, 1917. This application filed September 21,

' 1918. Serial No. 255,026.

To all whom it may concern:

Be it known that I, EDWARD II. HOBBIE, a citizen of the United States, residing at Boonton, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Headlights, of which the following is a full, clear, and

exact description.

This invention relates to headlights and the like, especially headlights for automobiles,and pertains more particularly to the type employing a concave reflector. In most cases the reflector is a paraboloid, and a concentrated light-source is placed at its focus. Theoretically, in such a lamp the reflected rays are projected in parallelism to the axis of the paraboloid. In practice the light source is not concentrated to a point but has an appreciable size and the reflecting surface is not a true paraboloid, and hence the rays of the projected beam are not truly parallel. Nevertheless, theoretical conditions are sufficiently approximated to produce the effect commonly known as glare.

The object of my present invention is to provide a headlight in which the highly objectionable glare is markedly diminished if not eliminated. Another object is to provide a headlight in which the rays composing the upper portion of the projected beam will be bent or deflected downwardly so as to aid in illuminating the roadway instead of being projected uselessly into the air and into the eyes of an approaching pedestrian or driver.

In carrying out the invention in its preferred form I provide a paraboloidal reflector and a concentrated light source in the axis of the paraboloid, the light-source being usually an incandescent electric lamp having a relatively small filament. In front of the reflector and closing the same is a sheet of glass, the upper portion of which (above a horizontal line, preferably the horizontal diameter) is composed, in effect, of a plurality of transverse prisms of triangular cross section. The lower portion of the glass (or lens, headlight glasses are now commonly called) is composed of a plurality of vertical ribs, of substantially cylindrolenticular cross section. With such a lens, the rays of the upper portion of the beam are refracted downwardly without (in theory) affecting their parallelism with respect to the vertical plane; while the lower rays of the beam are refracted laterally so as to broaden the lower part of the beam without (in theory) affecting the parallelism of the rays relative to thehorizontal plane. In this way the lower rays illuminate the sides of the roadway, while the upper rays give stronger illumination to the center of the roadway a greater distance ahead.

The embodiment outlined above is illustrated, somewhat diagrammatically, in the annexed drawings, in which- Figure 1 is a longitudinal section of a headlight in which my improvement is employed.

Fig. 2 is a rear View of the lens, showing the horizontal and vertical ribs or prisms.

Fig. 3 is a detail vertical section of the upper portion of the lens.

Fig. 1 is a detail horizontal section of the lower portion of the lens:

Referring to the drawings, 10 designates the paraboloidal reflector, and 11 is the lightsource located at or near the focus of the paraboloid, said source in the present instance being represented as an incandescent electric lamp. The lens 12 is a glass plate of circular form, having its outer surface plane. The upper portion of its inner surfaces is composed of a plurality of transverse parallel prisms 13 of triangular cross section, arranged with their bases downward. The lower portion of the inner surface is composed of a plurality of vertical ribs 1 1. In general, each rib consists of two triangular prisms arranged base to base, but in practice I prefer to round off the edges of the ribs and the hollows or grooves between the same, producing a wavy form of cylindro-lenticular prisms as indicated in Fig. 4. Preferably the line of division between the two portions is the horizontal diameter of the lens.

The effect of the prisms upon the rays forming the upper portion of the reflected beam of light is illustrated in Figs. 1 and 3.

The rays 1 5, 16, 17, 18, 19, 20 proceed from the reflector in more or less parallel paths (assuming that the light-source is at the focus) and but for the lens 12 they would continue beyond the reflector in the same directions,- as indicated by the dotted lines.

The prisms 13, however, refract the rays downwardly, as indicated by the solid lines.

The effect of the prismatic cylindro-lenticular ribs on the lower portion of the lens is illustrated in Fig. 4, the rays 21, 22, 23, 24, 25 being refracted laterally to right or left as the case may be. Of course the comparatively few rays that strike the surface at right angles, as at the apex of a rib or at the bottom of a hollow, for example rays 26, 27, are transmitted without refraction.

In every headlight of the type illustrated a certain part of the light is not reflected but proceeds toward the front in the form of a cone. What percentage of the total light this unrefiected portion is, depends, in general, upon the ratio of the radius of the mouth of the reflector to the distance from the light-source to the plane of the reflector mouth. Thus with a headlight in which the aforesaid radius is 6 inches and the said distance from the light source is 7 the ratio is .86, nearly, which is the tangent of one-half of the angle at the apex of the cone of unreflected rays. The corresponding angle is 40.5", roughly, which means hat the unreflected rays are only a little more than twenty per cent. of the total amount of light emitted from the source. With a reflector shallow enough to make the light-source only live inches from the lens the unreflected rays are only thirty per cent. of the whole. t will thus be seen that even if the lens allowed these rays to pursue their original paths they would, in many, probably in most, cases be so small a proportion of the total light as to cause none of the objectionable glare. With my lens, however, this cone of "eye is broken. up and diffused.

The amount of refraction produced by the lens upon any given ray is governed, of course, by the well known optical laws, and is, in general, determined by the angularity of the prismatic refracting elements and by the refractive index of the glass. These factors, however, can be varied considerably. With a good quality of glass such as used in making plate glass, having a refractive index of about 1.50, good results are obtained by making the refractive angles a, Fig. 3, about 9 and the refractive angles l), 4, about 8. The upper, or horizontal, prismatic elements I make about oneeighth' of an inch in height, and the lower, or vertical, prismatic elements I make about oneeighth of an inch from crest to crest, or from trough to trough, but these dimensions may be varied within wide limits without departing from the invention. Preferably neither angle (4 nor angle Z) exceeds 15.

Generally speaking, the most satisfactory results in use are obtained with the lightsource located slightly back of the focus of the paraboloid. If the horizontal ribs are below the vertical ribs the light should be slightly in front of the focus.

The lens can, of course, be made of optical glass, free from internal stresses and strize, with its surfaces accurately ground and polished, but the cost in such case would be prohibitively high. A lens capable of giving results entirely satisfactory in practice can be made by rolling out a mass of plastic glass to sheet form on a bed or table having a surface of the proper configuration, or on a plane bed or table by means of a ribbed roller. After the usual annealing the sheet or plate can be cut up into circular disks of the desired size or sizes.

It is evident that the refractive effect would be increased by the provision of re fracting elements on both surfaces of the lens, but it is in general sufficient to have them on one surface. In such case placing the plane surface outward facilitates cleaning of the lens.

It is to be understood that the invention is not limited to the specific details herein described, but can be embodied in other forms without departing from its spirit defined by the appended claims.

1 claim 1. In a headlight, the combination of a paraboloidal reflector, a concentrated lightsource in the reflector and in the axis thereof adjacent to the focus, and a lens closing the reflector, composed of a flat plate of glass, provided with a series of horizontal refracting elements arranged one above the other to refract light-rays downwardly, and provided on another portion with a series of vertical cylindro-lentieular refracting elements arranged side by side to retract light-rays laterally in both directions, the refractive angles of both the horizontal and the vertical elements being not greater than about 15 and one series of elements being above the other series, as set forth.

2. In a headlight, the combination of a paraboloidal reflector, a concentrated lightsource in the axis of the reflector and adjacent the focus thereof, and a lens closing the reflector, composed of a flat plate of glass, provided on its upper portion with a series of horizontal refracting elements arranged one above the other to refract light-rays downwardly, and on its lower portion with a series of vertical cylindro-lenticular refracting elements arranged side by side to refract light rays laterally in both directions, the refractive angles of both the horizontal. and the vertical elements being not greater than about 15, as set forth.

3. A headlight lens comprising a Hat plate of glass provided with a series of horizontal refracting elements to refract light rays downwardly, and provided on another portion with a series of vertical cylindro lenticular refracting elements arranged side by side and to refract light rays laterally in both directions, the refractive angle of both the horizontal and the vertical elements being not greater than about 15 and one series of elements being above the other series as set forth.

4;. A headlight lens, comprising a flat plate of glass provided with a series of horizontal refractive elements arranged one above the other to refract light rays downwardly, and provided on another portion With a series of vertical refracting elements arranged side by side to refract light rays laterally in both directions, the refractive angles of both the horizontal and the vertical elements being not greater than about 15, one of said series of elements being above the other as set forth, and said horizontal and vertical ele ments and flat lens being adapted to give a fixed dispersion of light passing through the lens at varying distances from the center thereof.

In testimony whereof I hereunto a'lfix my signature.

EDWARD H. HOBBIE. 

